🚨 Diagnostic Profile
Vehicle Make: Chevrolet (CHEVY)
Fault Description: Throttle Position Sensor PWM Signal High. This condition indicates the throttle position sensor (TPS) or its associated throttle body signal circuit is reporting a PWM (pulse-width modulated) signal value above the expected operating range, which the engine control module interprets as an invalid throttle position reading.
Vehicle Details: Chevrolet vehicle equipped with an electronic throttle control (ETC) system using a PWM-type throttle position signal; confirm exact model year and engine during intake to match correct connector and ECM pinout.
🚨 Repair Difficulty Tier
Tier: Intermediate
Throttle position sensor diagnosis requires scan tool data review, electrical circuit testing, and possible throttle body service. Most inspection steps are accessible to a trained technician, but accurate signal verification and relearn procedures require a capable scan tool and access to vehicle-specific service information.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify battery voltage and charging system output are within specification: battery should read approximately 12.4-12.8V key-off and 13.5-14.7V with engine running; low or unstable system voltage can cause false PWM signal faults.
- Visually inspect the throttle body electrical connector for corrosion, bent or spread pins, moisture intrusion, or a loose/incomplete connector lock at the throttle body housing.
- Inspect the wiring harness between the throttle body and the engine control module for chafing, pinched sections, or heat damage along its routed path near the intake and engine mounts.
- Check for any related diagnostic trouble codes and freeze frame data, including codes for throttle actuator control, TPS correlation, or accelerator pedal position; record all stored and pending codes before clearing anything.
- Confirm the throttle body bore and blade are free of carbon buildup or debris that could cause binding or restrict full blade travel, which can skew sensor output at the extremes of travel.
Step 2: Diagnostic Verification
- Connect a scan tool capable of reading manufacturer-enhanced data and monitor throttle position sensor PIDs (TP1, TP2, and Accelerator Pedal Position PIDs) with key on engine off, then during a slow manual throttle sweep from closed to wide open, watching for smooth linear transition with no flat spots, dropouts, or voltage/duty-cycle spikes.
- Compare primary and secondary TPS signal values against each other across the full sweep; on PWM-signal systems the duty cycle should move proportionally and inversely between the two sensor halves per the factory correlation table, rather than matching a single fixed voltage.
- Perform a backprobe test on the TPS signal circuit at the throttle body connector using a digital multimeter or lab scope (do not pierce wire insulation) to confirm signal activity is present and changing smoothly at both the sensor and, where accessible, at the ECM connector.
- Check the 5V reference and low-reference (ground) circuits for proper values and continuity using a digital multimeter against a known good chassis/engine ground; reference voltage should be a stable 5V with the key on.
- Measure circuit resistance and check for shorts to power or ground on the signal wire with the connector disconnected and key off, comparing readings to an unaffected like circuit if available.
- Verify the sensor reading is consistent and repeatable across multiple full throttle sweeps without dropouts, noise, or erratic duty-cycle spikes that would indicate an intermittent connection or failing sensor element.
Step 3: Resolution & Reset Process
- If the throttle body fails specification testing or shows mechanical binding, carbon buildup affecting blade movement, or an out-of-range/erratic PWM signal, clean the throttle bore with approved throttle body cleaner (avoid spraying directly into the sensor or motor assembly) or replace the throttle body assembly per vehicle-specific service information.
- If wiring faults are confirmed, repair the harness using approved weatherproof splice connectors and heat-shrink or soldered methods matching OEM standards, then verify continuity and signal integrity afterward.
- If the ECM is suspected, confirm all sensor, connector, and wiring causes are ruled out before replacement, and check for any applicable ECM software calibration updates through a factory-level scan tool.
- Perform the electronic throttle body relearn/idle learn procedure using a capable scan tool per the vehicle-specific service procedure; this typically involves a key-on engine-off relearn sequence or an idle relearn following battery disconnect or throttle body replacement, and is required any time the throttle body is replaced, cleaned, or the ECM is reprogrammed.
- Clear all diagnostic trouble codes and perform a test drive covering varied throttle inputs and idle conditions to confirm the fault does not return and that all OBD-II readiness monitors complete.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- Throttle body assembly (includes integrated TPS on most electronic throttle control systems): OEM or quality aftermarket unit matched to engine and model year
- Electrical connector, terminals, dielectric grease, and harness repair materials, if required
- Scan tool with manufacturer-level bi-directional control and throttle relearn capability (factory-level tool or high-end aftermarket scan tool with OEM-equivalent software)
- ECM reprogramming or calibration update, if a technical service bulletin applies to the specific model/year/engine combination
Average Component Price:
- Throttle body assembly: approximately $150-$450 for the part depending on model and OEM vs. aftermarket sourcing
- Throttle position sensor, if sold separately (uncommon on most modern integrated ETC throttle bodies): approximately $50-$150
- Harness and connector repair materials (connector pigtail, terminals, sealant): approximately $20-$80
Estimated Labor Hours:
- Diagnostic and inspection time (scan, visual inspection, circuit testing): approximately 0.5-1.5 hours
- Component replacement and relearn procedure (throttle body R&R plus relearn): approximately 0.5-1.0 hour, higher if intake or air cleaner components require removal for access
- Verification test drive and code clearing: approximately 0.2-0.5 hour
- Estimated total shop labor: approximately 1.2-3.0 hours depending on access difficulty and whether harness repair or ECM programming is also required
- Dealer or independent shop diagnostic fee (if separate from repair labor): typically $100-$180